As discussed above, the faintest radio galaxies should be detectable in
the submm waveband if the far-IR-radio correlation
remains valid at high redshifts. The narrow dispersion of this
correlation suggests that submm galaxies and faint
radio galaxies are perhaps the most likely populations of high-redshift
galaxies to overlap substantially.
Surveys made using SCUBA to search for optically-faint, and thus
presumably high-redshift, galaxies with radio flux densities close to
the detection threshold of the deepest radio surveys
(Barger et al., 2000;
Chapman et al., 2001b)
have been used to detect many tens of high-redshift
dusty galaxies much more rapidly than blank-field surveys.
The selection effects at work when making a radio-detected,
optically-faint cut from a radio survey are not yet sufficiently well
quantified to be sure that these catalogs are representative of all
submm galaxies. The typical optical magnitudes of the radio-selected
objects with submm detections are clustered around
I 24 and
greater. Hence, bright optical counterparts to
mJy-level submm galaxies are rare
(Chapman et al., 2002b).
Because relatively accurate positions are
available from the radio observations, it should be possible to
determine spectroscopic redshifts for a significant number of these
galaxies, providing a valuable contribution to our knowledge of the
distances to at least a subset of submm galaxies.